ordipointlabel {vegan} | R Documentation |
The function ordipointlabel
produces ordination plots with
points and text label to the points. The points are in the exact
location given by the ordination, but the function tries to optimize
the location of the text labels to minimize overplotting text. The
function may be useful with moderatly crowded ordination plots.
ordipointlabel(x, display = c("sites", "species"), choices = c(1, 2), col = c(1, 2), pch = c("o", "+"), font = c(1, 1), cex = c(0.8, 0.8), add = FALSE, ...)
x |
A result object from ordination. |
display |
Scores displayed in the plot. |
choices |
Axes shown. |
col, pch, font, cex |
Colours, point types, font style and
character expansion for each kind of scores displayed in the
plot. These should be vectors of the same length as the number of
items in display . |
add |
Add to an existing plot. |
... |
Other rguments passed to points and
text . |
The function uses simulated annealing (optim
,
method = "SANN"
) to optimize the location of the text labels
to the points. There are eight possible locations: up, down, sides
and corners. There is a weak preference to text right above the
point, and a weak avoidance of corner positions. The exact locations
and the goodness of solution varies between runs, and there is no
guarantee of finding the global optimum. The optimization can take a
long time in difficult cases with a high number of potential
overlaps. Several sets of scores can be displayed in one plot.
The function is modelled after pointLabel
in
maptools package (which has chained dependencies of S4
packages).
The function returns invisibly an object of class
ordipointlabel
with items xy
for coordinates of
points, labels
for coordinates of labels, items pch
,
cex
and font
for graphical parameters of each point or
label. In addition, it returns the result of optim
as
an attribute "optim"
. The unit of overlap is the area
of character "m"
, and with variable cex
it is the
smallest alternative. The result object inherits from
orditkplot
result, and can be replotted with its
plot
command. It may be possible to further edit the result
object with orditkplot
, but for good results it is
necessary that the points span the whole horizontal axis without empty
margins.
The function is designed for ordination graphics, and the optimization works properly with plots of isometric aspect ratio.
Jari Oksanen
See pointLabel
for references.
pointLabel
for the model
implementation, and optim
for the optimization.
data(varespec) ord <- cca(varespec) ordipointlabel(ord)